The long term goal of this research is to elucidate the pathogenic mechanisms of and protective host responses to trichomonad membrane and extracellular proteinases. Trichomoniasis is a prevalent sexually transmitted human and bovine disease for which there is no laboratory animal model of reproductive tract infection. Tritrichomonas foetus proteinase was chosen for study because of evidence that it is a virulence factor. Moreover, this organism offers a unique opportunity to test potential immune defense mechanisms in vivo in the natural host, cattle. Recently we showed that the T. foetus extracellular proteinase cleaves proteins involved in defense of the reproductive tract, such as IgG1, IgG2, lactoferrin, fibronectin and fibrinogen. After characterizing the extracellular proteins (which is also present in T. foetus membranes), we have partially purified the enzyme. Therefore, we are now in a position to further characterize its role in virulence and the ability of antiproteinase antibody to neutralize enzymatic activity. The latter is of special interest because others have shown antiproteinase antibody to protect sheep against disease caused by Bacteroides nodosus. To further study the role of the T. foetus extracellular/membrane proteinase in pathogenesis and the role of antibodies to proteinase protection, we propose to: 1) Investigate specific potential pathogenic mechanisms of trichomonad proteinase (ability to cleave different allotypes of IgG2, to lyse nucleate cells or rbcs and to promote adherence of T. foetus to cells). 2) Clone, express and characterize the gene(s) for T. foetus proteinase. This will include Southern blots to determine whether the gene is conserved in T. foetus isolates and whether it is present in T. vaginalis. 3) Produce and characterize antibody against T. foetus semipurified and/or recombinant proteinase. 4) Determine whether antibodies to T. foetus proteinase will neutralize the enzyme and interfere with functions correlated with virulence. If appropriate, ability to neutralize T. Vaginalis proteinase will be tested also. This research should provide new insights into virulence mechanisms of T. foetus and host defense mechanisms. Since T. vaginalis also produces extracellular proteinase, the data may have broader application to an important human sexually transmitted infection.